The present invention relates to a high-speed burnishing drill including a reamer section which has secondary cutting edges formed of diamond chips.
There are known various types of drilling tools that are adapted to ream a hole to a desired diameter while at the same time cutting the wall to form the hole. Such a drilling tool is a single-purposed, exclusive and/or automated tool which can be of increased cutting efficiency and used to provide high quality and uniform products.
Japanese Utility Model Laid-Open Application No. 62-65107 discloses a reamer section drill including two drilling edges and four reaming edges, all these edges being arranged in the same circle.
FIGS. 4 and 5 in the accompanying drawings show another known burnishing drill. Such a burnishing drill comprises a cylindrical drill body 2 connected with a shank 1. The drill body 2 has formed at a tip 3 thereof cutting edges 5 that are opposed to each other diametrically about the longitudinal axis of the drill body 2. Each of the cutting edges 5 has associated therewith an inclined or slant face 6 extending therefrom rearwardly with respect to the direction of rotation (shown by arrow A in FIG. 5) and a guide face 7 axially extending from the radially outer edge of the slant face 6. The drill body 2 further includes respective longitudinally extending relief surfaces 8 formed between each of the cutting edges 5 and the corresponding guide face 7 at the outer wall of the drill body 2 and longitudinally extending relief grooves 9 formed in the drill body 2.
This drill does not have good centering and stabilizing properties since the initial bite cannot be made properly. As a result, a hole drilled by such drill will be reamed excessively and its inner wall will be rough.